Slip, Sliding Away

Earthquakes are caused by forces deep within the Earth's crust. As continents collide, ocean floors split, magma flows, volcanoes erupt and other natural processes occur pressure is released making vibrations within the ground which we call earthquakes. Where one block of the Earth's crust interacts with another they may slip, slide or push each other resulting in a fault. This movement in the Earth is called tectonics. The interior of Mars has very little movement and does not have quakes that have been measured.

A fault is a fracture in the Earth's crust where two blocks of crust have slipped against each other. In the diagram at right figure A is a Normal Fault where the blocks are pulled apart allowing for one block to slip down on the other. Figure B indicates a Thrust Fault which occurs when blocks are pushed against each other raising one of the blocks. A Strike-Slip Fault, figure C, occurs when stress causes the blocks to move horizontally past one another. (Diagram adapted from a USGS diagram.)

The severity of an earthquake is related to magnitude, that is, the seismic energy recorded on a seismograph and intensity meaning the observed effects that the ground shaking has on people, buildings, man-made structures and natural features. The epicenter of an earthquake is the spot on the surface directly above the area where the quake took place. The focus or hypocenter is the area inside the Earth where the event happened.

The Plasma Dictionary is based on the Fusion & Plasma Glossary that was originally created on FusEdWeb, Fusion Energy Educational Website which has additional introductory information on plasma and fusion science .

A planet (from the Greek planete means "wanderer" or
more forcefully "vagrant, tramp") is an object in orbit around a star
that is not a star in its own right. Much like "continent," "planet"
is a word without a precise definition, with history and culture playing
as much of a role as geology and astrophysics

This is a "living glossary". This means that the glossary may grow every week as individuals submit new entries. This has been set up as a class resource for CEM-181H, the freshmen honors chemistry lecture at Michigan State University.